class Compiler {
  constructor (vm) {
    this.el = vm.$el;
    this.vm = vm;
    this.compile(this.el);
  }
  // 编译模板 处理文本节点与元素节点
  compile (el) {
    let childNodes = el.childNodes;
    Array.from(childNodes).forEach(node => {
      // 处理文本节点
      if (this.isTextNode(node)) {
        this.compileText(node);
      } else if (this.isElementNode(node)) {
        this.compileElement(node);
      }

      // 判断node节点是否有子节点，如果有子节点，要递归调用compile
      if (node.childNodes && node.childNodes.length) {
        this.compile(node);
      }
    })
  }
  // 编译元素节点，处理指令
  compileElement (node) {
    // console.dir(node)
    Array.from(node.attributes).forEach(attr => {
      let attrName = attr.name;
      if (this.isDirective(attrName)) {
        // v-text --> text
        attrName = attrName.substr(2);
        let eventName = undefined;
        if (attrName.startsWith('on')) {
          [attrName, eventName] = attrName.split(':');
          // attrName = attrName.replace(/(\:\w{1})/, $1 => {
          //   return $1.slice(-1).toUppercase();
          // })
        } 
        
        let key = attr.value;
        this.update(node, key, attrName, eventName);
      }
    })
    //判断是否是指令
  }
  update(node, key, attrName, eventName) {
    let updateFn = this[attrName + 'Updater'];
    updateFn && updateFn.call(this, node, this.vm[key], key, eventName)
  }
  textUpdater(node, value, key) {
    node.textContent = value;
    new Watcher(this.vm, key, newValue => {
      node.textContent = newValue;
    })
  }
  // v-model
  modelUpdater (node, value, key) {
    node.value = value;
    new Watcher(this.vm, key, newValue => {
      node.value = newValue;
    })
    // 双向绑定
    node.addEventListener('input', () => {
      this.vm[key] = node.value;
    })
  }
  // v-html
  htmlUpdater (node, value, key) {
    node.innerHTML = value;
    new Watcher(this.vm, key, newValue => {
      node.innerHTML = newValue;
    })
  }
  // v-on
  onUpdater (node, value, key, eventName) {
    if (!eventName) return;

    const eventArr = eventName.split('.');
    const tempKey = key.replace(/\)/, '').split('(');
    node.addEventListener(eventArr[0], e => {
      if (eventArr.includes('prevent'))  e.preventDefault();
 
      const $event = tempKey[1] === '$event' ? e : undefined;
      this.vm.$options.methods[tempKey[0]] && this.vm.$options.methods[tempKey[0]].call(this.vm, $event);
      
      if (eventArr.includes('stop'))  e.stop();
    })
  }
  // 编译文本节点，处理插值表达式
  compileText (node) {
    let reg = /\{\{(.+?)\}\}/;
    let value = node.textContent;
    if (reg.test(value)) {
      let key = RegExp.$1.trim();
      node.textContent = value.replace(reg, this.vm[key])
      // 创建watcher对象
      new Watcher(this.vm, key, (newValue) => {
        node.textContent = newValue
      })
    }
  }
  // 判断元素属性是否是指令
  isDirective (attrName) {
    return attrName.startsWith('v-')
  }
  // 判断节点是否是文本节点
  isTextNode (node) {
    return node.nodeType === 3;
  }
  // 判断节点是否是元素节点
  isElementNode (node) {
    return node.nodeType === 1;
  }
}